It has long been known to utilize the effect of gravity on fluids having different densities to determine the levelness of elements such as building components, machines, lines, poles, etc. Spirit levels, also called bubble levels, are well known instruments utilizing gravity in this way to set horizontal or vertical surfaces. Such levels include a sealed vial containing a bubble, typically air, floating in a non-freezing liquid, usually mineral spirits. The measured surface is considered horizontal or vertical when the air bubble rests between predetermined graduated marks on the vial.
The accuracy with which a horizontal or vertical plane can be determined is critically dependent on the accuracy at which the bubble is centered between the transverse marks on the vial which, of course, is dependent on the visibility of such lines and the outline of the bubble itself. While the position of the bubble can readily be seen under normal lighting conditions, it becomes difficult to see on a heavily clouded day, or at dusk, or in poorly lighted spaces. That is to say, typical conventional levels can be effectively used only in relatively well-lighted environments and, accordingly can put constraints on the times and places craftsmen such as carpenters and bricklayers are able to work efficiently.
Because it is frequently necessary to measure or set the levelness of a horizontal surface or to set or plumb a vertical surface in less than ideal conditions for locating the position of the bubble in the vial there have been many attempts to provide a level having a more easily located bubble. For instance, others have provided an illumination device in the level to illuminate the vial to enhance visibility of the bubble. Another attempt to enhance bubble visibility included the use of a floating object within the vial. Still other attempts have utilized complicated electrical or fiber optic sensing of the bubble position.
Each of these prior art attempts have failed to provide a simple and inexpensive, yet successful method of overcoming bubble-locating problems. For example, bubble illumination devices may work well in dark conditions, but they provide little assistance when operating in dimly lit or more well lit areas in which the bubble may blend in with the background when viewing the vial. Floats may increase visibility, but their inclusion in the vial often results in less precise measurements. Levels including electrical and fiber optic sensing means are typically too expensive and too sensitive to be handled easily at work sites and may not provide any enhancement to viewing the bubble in certain conditions.
Therefore, there is a need for an improved vial and level which provide increased visibility of the bubble to aid in the location of the bubble during measurements. Furthermore, there is a need for such an improved vial and level which do not require special handling at work sites and which do not require significant additional costs of manufacturing. In addition, there is a need to provide a vial and level which operate well in a variety of lighting conditions and which provide for easy location of the bubble within the vial.